This tallies in with the HAL version, which is that T5 baggage reclaim is currently blocked due to a BA's Resource Management system outage, not a HAL outage. This outage has resulted in mass congestion of bags the baggage area. "Due to delays collecting bags from outputs in the Main Baggage Hall, congestion is being seen on the sorters as bags recirculate while unable to output due to full lateral belts. As such, check-in and transfer inputs in T5 have been brought to a controlled stop to manage the inbound volume of product into the T5 System as a temporary measure". In other words, the system that tells BA ground staff to "go to gate 535 and collect 6 ULDs from the inbound flight from DEL" isn't working. There are now several thousand bags affected, and I think T3 is also partly affected too, but they have a bit more scope for manual working than T5.

HAL are also advising passengers to go home and submit online requests for baggage return. This started about 14:00 hrs, but it took a while for the critical mass to happen and thus stop operations.

I'm speculating here, but this also means that it's going to inhibit outbound services since the bags inbound won't have been offloaded (?).